1. Field of the Invention
The present invention relates to an apparatus for controlling a continuously variable transmission (CVT) used in a vehicle.
2. Description of the Prior Art
A CVT capable of continuously controlling a speed ratio e (=output side rotational speed Nout/input side rotational speed Nin) is used in a vehicle as a power transmission unit with an excellent specific fuel consumption. A desired engine speed Ne' is set as an engine speed to achieve an output horse power of the engine set as a function of a pedalling amount of an accelerator pedal for example with a minimum fuel consumption, and the CVT is controlled such that an actual engine speed Ne is equalized to the desired engine speed Ne'. In the prior method of controlling the CVT, the speed change of the CVT, i.e. the alteration in the speed ratio e is always effected when there is some deviation between Ne and Ne', while the transmission loss of the CVT is so large during the speed change that disadvantages are encountered in both the specific fuel consumption and driveability of the engine. Also in the prior CVT, when a throttle valve is fully opened to accelerate a vehicle, the engine speed Ne reaches the maximum value resulting increased noise due to the reduction of the speed ratio e prior to the increase of a vehicle speed V.